Online ISSN : 1883-7204
Print ISSN : 0021-4787
ISSN-L : 0021-4787
Volume 48 , Issue 10
Showing 1-21 articles out of 21 articles from the selected issue
  • Shiko Saikawa, Masahiro Kobayashi, Takeshi Araya
    1979 Volume 48 Issue 10 Pages 748-755
    Published: October 05, 1979
    Released: August 05, 2011
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  • Seishin Kirihara, Katsuyuki Imai, Isao Masaoka, Ryoichi Sasaki
    1979 Volume 48 Issue 10 Pages 756-762
    Published: October 05, 1979
    Released: August 05, 2011
    This report covers experimental results on the relation between welding methods (natural cooling and inside water cooling) and residual stress and carbide precipitation in heat affected zone of 2B, 3B, 4B, 8B and 12B welded austenitic stainless steel pipes.
    The results of this experiment are as follows:
    (1) The inside surfaces of pipe welds by natural cooling show tensile residual stress.
    (2) The inside surface of pipe welds with inside water cooling in appropriate conditions show compressive residual stress.
    (3) The weld sensitized zone of pipe welds can be reduced by inside water cooling technique. From the above results, it is considered that the inside water cooling method is effective to prevent SUS 304 pipe weldment from stress corrosion cracking.
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  • Riei Ichikawa, Teruo Ohashi
    1979 Volume 48 Issue 10 Pages 763-769
    Published: October 05, 1979
    Released: August 05, 2011
    The properties and problems of spot welding commercial pure titanium to some aluminum alloys (1100-H14, 5052-H34 and 6061-T4) are examined by means of tensile shear test and macroor micro-structural observations. The results obtained are as follows:
    1) The spot welded joints of titanium-1100, -5052 and -6061 aluminum are ductile and each tensile shear strength reaches about 150, 320 and 300 kg/spot, respectively.
    2) The bonding of titanium to aluminum is accomplished in a manner of brazing.
    3) It is shown that there is not any intermetallic compounds such as TiA13 in the welded joints regardless of the mutual diffusion of Ti and Al through the bonding interface.
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  • Toshio Enjo, Kenji Ikeuchi, Naofumi Akikawa
    1979 Volume 48 Issue 10 Pages 770-775
    Published: October 05, 1979
    Released: August 05, 2011
    Diffusion welding of copper to aluminum has been carried out in vacuum. The microstructure of the bonding zone was examined in detail with several metallographic methods to make clear the important factors which affect the mechanical properties of the joint. Results obtained are summarized as follows:
    1) An intermetallic compound layer was observed which could be devided into characteristic region I, II, and III. The intermetallic compounds of θ and γ2 formed in I and III region, respectively. The hardness of II region is the highest of the regions.
    2) The growth of the intermetallic compound layer is considered to be controlled by the atomic diffusion and the increase in the intimate contact area between the faying surfaces. The diffusion process became more important with the increase in welding temperature and time.
    3) At shorter welding time, the tensile strength of joints increased with the rise of welding temperature, time, and pressure. This stage is considered to be a process where the intimate contact between the faying surfaces was developed.
    4) At longer welding time, the tensile strength of joints approached to a saturated value (2.3 kg/mm2) much lower than that of aluminum base metal. This tendency was observed for the thickness of the intermetallic compound layer greater than 15-20μm. In this case, fracture was developed in the intermetallic compound layer, but not at the welding interface. The strength of these joints is considered to be controlled by the intermetallic compound layer.
    5) Oxide film of aluminum delayed the real metallic contact between the faying surfaces at shorter welding time.
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  • Kimiyuki Nishiguchi, Takayoshi Ohji, Hiroaki Takebayashi
    1979 Volume 48 Issue 10 Pages 776-780
    Published: October 05, 1979
    Released: August 05, 2011
    The equilibrium and stability of molten pool in I-butt welding are discussed under the condition that arc pressure is negligibly small. The critical molten pool size for Rayleigh-Taylor Instability is made clear and compared with the permissible molten pool size, derived from the static equilibrium of surface tension and gravity.
    In conclusion, the critical size of molten pool in flat positional welding without backing can be explained by the disturbance of the above mentioned static equilibrium. On the, other hand, the molten pool phenomenon in overhead positional welding is disturbed by Rayleigh-Taylor Instability.Consequently, in order to avoid this instability, it is necessary to limit the molten pool to small size at this position.
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  • Takeshi Nishi, Shoji Saito, Taketo Nakano, Yukihiko Horii
    1979 Volume 48 Issue 10 Pages 781-786
    Published: October 05, 1979
    Released: August 05, 2011
    The 40 % Ni type weld metal is undermatching for 9 % Ni steel with regard to static tensile strength. In this case, the tensile strength of welded joints is influenced remarkably by strength of weld metal and base metal, and by the welding conditions such as heat input, groove shape and so on. Welded joint performance tests were carried out, in this report, to investigate the static tensile strength of MIG welded joints of 9 % Ni steel with 40 %Ni type weld metal. Main experimental results are summerized as follows:
    (1) The transverse tensile strength of welded joints increases with decreasing relative thickness (average width of weld metal/plate thickness). Therefore, it is beneficial, both for increasing strength and for improving efficiency, to narrow the groove as far as possible according to the plate thickness.
    (2) The transverse tensile strength of welded joints decreases with increasing welding heat input; but, in case of vertical position, it is possible to obtain 66.8 kg/mm2 (95 Ksi) or more within heat input of 35 KJ/cm.
    (3) It may be considered that, in case of multi-pass weld metal, the strength of intermediate pass weld metal has increased due to the precipitation hardening caused by the fine carbides of molybdenum and chromium.
    (4) It was confirmed by center-notched wide plate tension test that the weld metal and fusion zone possess a satisfactory cryogenic fracture toughness as all the fracture occurred in a high-stress ductile manner with fracture stress equal to the cryogenic strength of the 40 % Ni type weld metal.
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  • Wataru Shimada, Kazumichi Machida
    1979 Volume 48 Issue 10 Pages 786-792
    Published: October 05, 1979
    Released: August 05, 2011
    Characteristics of TIG arc and the fundamental melting behavior of base metal at low pressure atmosphere are studied in order to get a TIG arc of low arc pressure which is suitable for high speed welding. The results obtained are as follows;
    (1) Maximum arc pressure at the arc center is very small under low gas pressure condition. At the pressure of 32 mmHg, it reaches less than one tenth of that in atmospheric pressure.
    (2) A bright spherical zone, so called "Cathode Zone, " is clearly observed in low pressure arc just below the cathode electrode. It is highly ionized and acts as a distributed disk heat source for the melting of base metal.
    (3) The shape of cathode zone can be controlled arbitrarily by a water cooled nozzle. Also, current density and energy density of low pressure arc can be increased by the nozzle constriction without increasing of arc pressure.
    (4) Under low pressure condition, melting process is not influenced much by the arc pressure even at higher arc current. Metal flow in the molten pool gives much influences to the penetration shape, and is easily changed by the degree of concentration of arc heat source.
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  • Shuji Nakata, Masahiro Nishikawa, Hiroaki Agoh
    1979 Volume 48 Issue 10 Pages 793-799
    Published: October 05, 1979
    Released: August 05, 2011
    Projection diameter and height are adapted as factors which characterize a shape of a embossed projection. In this report, the effect of projection diameter on nugget formation and growth has been examined, using the various projections with the constant height, embossed on a cold rolling sheet of low carbon steel of 1 mm in thickness (SPCC).
    Shape of nugget formed without explosive splash at initial period of weld time corresponds to the diameter of cold collapsed area of projection and its pressure distribution. The critical current which is the minimum current required to form nugget increases with the diameter of cold collapsed area corresponding to the area of current path. Using the projection with a small diameter, small nugget is initially formed to grow larger, and on the other hand, using the projection with a large diameter, the contact part is heated like a torus at the initial period of weld time. The tensile sheare strength is related to the nugget diameter and the saturated diameter of nugget depends only on the weld current above the critical current as a function of the cold collapsed area and the electrode force. Using thr projection with a small diameter, the depression of embossed projection is difficult to become flat at the initial period of weld time, however, the indentation is more seriously affected by the splash.
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  • Yoshiaki Arata, Fukuhisa Matsuda, Yutaka Shibata, Yoshihisa Ono, Mitsu ...
    1979 Volume 48 Issue 10 Pages 799-807
    Published: October 05, 1979
    Released: August 05, 2011
    From a viewpoint of the practical use for electron beam (EB) welding, the penetration characteristics and the occurring region for weld defects were studied in various welding conditions for thick plate (50-100 mm) of the structural high strength steels, and nextly some mechanical and metallurgical characteristics of the deep-penetrated weld metal were made clear in this investigation. Moreover some problems of the EB-welding procedure in practical use were investigated by using 25 mm thick plate of SM50A. The remarkable conclusions are as follows;
    (1) The weld defects occurred in the thicker materials were divided into two main classes, that is, the vertical crack-like center and bottom defects in the stand point of the occurred location in the deeppenetrated weld metals. The former often occurred nearly in ab; 1.0, and the latter occurred in ab>1.3 or <0.5. Besides the crack-like center defect sometimes switched over to the cavern-like defect in case of the weld bead in a large weld heat input.
    (2) It was found that the sound weld metal without defect, the penetration depth of which is 7577 mm, was obtained nearly for ab; 0.7 in case of 27KW beam power. The regions for the sound weld metal obtained tended to be expanded with a decrease of the beam power.
    (3) There is no obvious variation in the oxygen and nitrogen contents between the base and weld metals, or between the face and bottom parts of deep-penetrated weld metal. Furthermore the Mn content in weld metal is decreased 10 % less than that in base metal according to the EPMA-analysis. The degree of the decrease tends to be decreased with an increase of the penetration depth for the analized location.
    (4) The impact strength of the deep-penetrated weld metal tends to be lowered in general with an increase of weld heat input, and the strength of the bottom part in the penetration showed higher value than that of the face part. Moreover the impact strength of EB-weld metal had a tendency to be increased with an increase of the hardness of it in general.
    (5) It was comfirmed to be possible to enlarge the allowable limit for groove opening and to improve the impact characteristics for EB-weld metal by using the cut wire as an insert material. Furthermore the allowable limits for groove condition in L joint were respectively clarified against the three levels of welding condition, the bead shape of which makes the wedge, well and wine-cup types.
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  • Shizuo Mukae, Mitsuaki Katoh, Kazumasa Nishio
    1979 Volume 48 Issue 10 Pages 808-813
    Published: October 05, 1979
    Released: August 05, 2011
    Suppressive effects of Ti and N to the austenite grain growth in weld heat affected zone of steels were investigated from a standpoint of the time exponent, n and the activation energy for boundary migration, Q in isothermal grain growth test. The results obtained are as follows. 1) Austenite grain growth of steels added together both Ti and N can be expressed by Beck's equation. 2) Value of n is remarkably influenced by the quantity of a insoluble Ti (or N) and independent of a soluble Ti (or N). 3) Value of Q is increased considerably in duplex addition compared with separate addition of Ti and N. In this case an extent of the effect of a soluble Ti (or N) to Q is a greater than a insoluble Ti (or N). 4) Grain size of austenite isothermaly heated can be estimated using coefficient of austenite grain growth which is decided by quantity of Ti and N added in steels.
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  • Tomohiko Shida, Hisanori Okamura, Hisanao Kita, Yoji Akutsu
    1979 Volume 48 Issue 10 Pages 813-820
    Published: October 05, 1979
    Released: August 05, 2011
    Horizontal position electron beam welding of heavy section 0.170-steel, 21/4 Cr-I Mo low alloy steel and 18 Cr-8 Ni steel plates up to 100 mm in thickness was investigated using a 42 kW (60 kV) high vacuum type welding machine.
    Penetration characteristics and occurrence and prevention of welding defects were discussed comparing horizontal position welding with flat position welding.
    It was concluded that,
    I. Partial penetration
    (1) Penetration depths in horizontal position were 15 to 20 % deeper than in flat position.
    (2) Voids occurred, when the penetration depth in horizontal position exceeded 50 mm and no oscillation was applied to the beam.
    (3) Effects of focus position on tendency of occurrence of welding defects and bead shapes in horizontal position were smaller than in flat position.
    (4) Lack of molten metal seemed to cause voids in horizontal position welding.
    II. Full penetration
    (1) Occurrence of voids in horizontal position was influenced by value and fluctuation of penetration current, and oscillation conditions of the beam.
    (2) Beam oscillation (X direction, 100 Hz) was effective to prevent void formation in full and partial penetration welding.
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  • Yoshiaki Futamura, Hiroshi Kamata
    1979 Volume 48 Issue 10 Pages 820-824
    Published: October 05, 1979
    Released: August 05, 2011
    It is discribed in this paper that the heigh sensitive inside crack growth monitor is studied and developed by using the electric resistance method from the outside surface of the piping. When the needle interval is equal to the pipe thickness, the monitor will have the best sensitivity. The limit of sensitivity is more less than 10 % of the pipe thickness. By using the detector with five needles, the correction for pipe temperature is carried out exactly. This method can be applied to the piping system, when it is difficult to decide whether the indication by the inservice inspection is flaw or not, or when the indication is seemed to be flaw in spite of very small indication. By applying the monitor in practice, it is expected to contribute to the increase in availability and reliability in the power reactor plant.
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  • Yoshihiko Mukai, Masato Murata
    1979 Volume 48 Issue 10 Pages 825-832
    Published: October 05, 1979
    Released: August 05, 2011
    The effects of plate thickness on crack propagation feature, particularly on crack branching, have been studied in stress corrosion cracking (SCC) of SUS 304 stainless steel in 42 % MgCl2 solution (143°C). Ktr I II, stress intensity factor at which the transition from region I to II occurs, decrease with decreasing of the plate thickness. And Ktr I II is accorded with Kb, stress intensity factor at the start of crack branching.
    The condition of start of crack branching is shown by the equation B-2ρH where B: Plate thickness, ρH: Radius of plastic zone at crack tip.
    As mentioned above, the crack branching in SCC with depend on the variation of three dimensional plastic deformation mode at crack tip.
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  • Michio Inagaki, Yoshiki Muramatsu, Kazuo Hiraoka
    1979 Volume 48 Issue 10 Pages 833-838
    Published: October 05, 1979
    Released: August 05, 2011
    The Cranfield type test is one of the popular tests for evaluating lamellar tearing of steel plates.
    The authors proposed the Z-direction Cranfield type test in which the welded beads are built-up in the through-thickness direction of plate.
    By the Z-direction Cranfield type test and the original test method (X-direction test), the relation between the shape and distribution of nonmetallic inclusions and the behavior and propergation of cracks can be made clear.
    Lamellar tear sensitivity of steel plates can be evaluated quantitatively with the relationship between the direction and the length of cracks.
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  • Toshiro Kikuchi, Iwao Onishi
    1979 Volume 48 Issue 10 Pages 838-845
    Published: October 05, 1979
    Released: August 05, 2011
    Effect of the impurity elements P, S, Sb, As, Sn on the sensitivity of steel to reheat cracking have been studied at the stress relaxation test. Furthermore, in the sample after reheat treatment, the segregation of impurity elements have been investigated at the Auger electron spectrometer.
    The results of the study obtained are summarized as follows:
    1) The increase of impurity elements P, S, Sb, As, Sn in steel was decreased extremely the plastic deformability Δlp', as measured at the time of occurrence of cracking, and was increased very the sensitivity to cracking.
    2) It has become apparent that the remarkable segregation to grain boundary of impurity elements P, S, Sb in steel occur in the range of temperature at the occurrence of reheat cracking.
    3) The mechanism of reheat cracking can be considered as follows:
    Toe of weld that occur the reheat cracking remain high tensile stress in order to stress concentration, and segregation to grain boundary of impurity elements P, S, Sb in steel is accelerated by its tensile stress, and as a result, grain boundary well be embrittlement. Farthermore, the plastic deformation in toe of weld has little in order to remain hardened structure and coarse grain. Consequently, it is considered that reheat cracking caused by the embritllement in grain boundary, hardened structure and coarse grain.
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  • Masaki Imachi
    1979 Volume 48 Issue 10 Pages 845-850
    Published: October 05, 1979
    Released: August 05, 2011
    In the previous paper, the keinetics of wetting and adhesion of various adherends by molton polyethylene in argon gas were investigated. In this paper, the keinetics of wetting and adhesion of glass plate by molten polyethylene containing 0.5 mm length glass fibers were investigated. Relation among wettability, adhesiveness and surface tension γL and viscosity η of this composite polyethylene was also studied.
    The results are summarized as follows:
    (1) It was experimentally confirmed that the time constant τ of cos θ-t curve obtained on plain polyethylene or the polyethylene which contains glass fibers is in proportion to η/γL, where θ is contact angle, and τ is mainly affected by the change η than that in γL, when the temperature changes.
    (2) According as polyethylene contains more glass fibers, τ and η increase and the rate of the increase of τ is far greater than that of η.
    (3) Because of the existence of glass fibers in polyethylene, wettability is reduced but the adhesive strength considerably increases and this is due to the fact that the cohesive failure occurs in the polyethylene layer and the polyethylene is reinforced by glass fibers.
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  • Yukio Ueda, Keiji Fukuda, You Chul Kim
    1979 Volume 48 Issue 10 Pages 851-858
    Published: October 05, 1979
    Released: August 05, 2011
    Restraint intensities of a slit in a rectangular plate were calculated, under two loading conditions; uniformly distributed loads along the slit and a uniform dislocation along the slit. The calculation was carried out by superposition of the analytical solution for an infinite plate and correction by the finite, element method to a rectangular plate. Furthermore, very accurate formulae for the restraint intensities were derived.
    The following conclusions were obtained:
    (1) For a specimen having the ratios of L/l≥1.5 and B/l≥1.8(L, B and l are the length, the breadth of the specimen and the length of the slit, respectively.), the restraint intensities can be easily obtained by the following equations.
    Rp(x)=(1-βp) E/2 h/l 1/√1-(2x/l)2 (uniformly distributed loads)
    Rδ(x)=[1-βδ(x)] E/π h/l 1/1-(2x/l)2 (uniform dislocation)
    where βp=0.6/(L/l)n+0.75/(B/l)1.82, n=5.8/(B/l)2+2.2
    βδ=[1-(2x/l)2δ0, βδ0δ(x=0)
    E; Young's modulus, h; plate thickness
    So, there is a clear relation between the two restraint intensities as shown in the following explicit from;
    Rp(x)/Rσ(x) = π/2 1-βρ/1-βδ √1-(2x/l)2
    (2)Dependencies of the restraint intensities on L/l and B/l are made clear and convergencies of the intensities to limiting values are studied when L/l or/and B/l becomes greater.
    (3) Effect of the ratio of throat thickness to plate thickness upon the restraint intensities is taken into account and a simple formula is derived.
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  • Kotoji Ando, Masaki Koshiro, Nobukazu Ogura
    1979 Volume 48 Issue 10 Pages 859-865
    Published: October 05, 1979
    Released: August 05, 2011
    A new test method to assess the susceptibility of coarse grained HAZ to hot straining embrittlement has been proposed. Hot straining embrittlement of the coarse grained HAZ in HT80, A533 and SM50 steels has been evaluated.
    Results can be summarized as follows:
    (1) The susceptibility of coarse grained HAZ to hot straining embrittlement can be easily assessed by using BNP specimen (three points bend specimen with notch of poor penetration) with angular distortion.
    (2) The degree of hot straining embrittlement has been analyzed quantitatively as a function of angular distortion of the joint.
    (3) The susceptibility to hot straining embrittlement in SM50 steel increases with increasing heat input of the joint.
    (4) Thermal stress relief has advantage effect on the coarse grained HAZ's fracture toughness in SM50 steel embrittled by hot straining, but it has disadvantage effect on the HAZ's fracture toughness in A533 steel embrittled by hot straining. For A533 steel, stress relief embrittlement is superposed on hot straining embrittlement.
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  • Eiji Takahashi, Kenji Iwai
    1979 Volume 48 Issue 10 Pages 865-872
    Published: October 05, 1979
    Released: August 05, 2011
    This research was conducted in order to clarify the cause of transverse cracks, which were observed in heavy section weldments by submerged arc process, and to investigate the possibility of prevention of them by use of low temperature postweld heat treatment. In the investigation, cracking tests were carried out on restraint test specimens with the thickness range of 50 mm through 200 mm. The characteristics of cracks were observed. Moreover, magnitude of residual stresses and concentration of diffusible hydrogen just after welding as well as after low temperature postweld heat treatment, both of which were considered to have close connection with the cause of the cracks, were measured experimentally and their effects on the occurrence of a crack were examined.
    The outline of the results obtained is as follows;
    (1) Transverse cracks initiate in the weld metals just below the final layer of welds and gradually propagate both to the top surface and to the bottom surface. Intergranular fracture generally appears in the initiation area of the crack and quasi-cleavage fracture appears in the propagation area.
    (2) The location of the largest residual stress parallel to the weld line corresponds to that of crack initiation and so does the location of the highest concentration of diffusible hydrogen just after welding. This implies that the transverse crack is a cold cracking induced by longitudinal residual stress and diffusible hydrogen.
    (3) The highest longitudinal residual stress is nearly constant in the range of plate thickness over 50 mm. Meanwhile, the highest concentration of diffusible hydrogen just after welding increases with an increase in plate thickness. It decreases with an increase in interpass temperature during welding or in temperature of postweld heat treatment and thereby the cracks can be arrested. Judging from the result, prevention of these cracks can be made possible only by decreasing diffusible hydrogen concentration through postweld heat treatment under lower temperature as compared with a conventional intermediate stress relief annealing.
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  • Yoshiaki Arata, Katsunori Inoue
    1979 Volume 48 Issue 10 Pages 873-878
    Published: October 05, 1979
    Released: August 05, 2011
    The stability of the light from arc plasma becomes a serious problem when we perform a various automatic control of arc welding on utilizing the image obtained by the light of arc. The fluctuating properties of the light are investigated on CO2 arc and their dependence on arc generated condition, their space distribution characteristics, the power density function and the amplitude density function of the fluctuating component are measured.
    The results are as follows;
    1) The new formula of power spectrum density function is introduced from the experimental results. This formula is decided by three parameters.
    2) Power of fluctuating component is obtained from the above mentioned experimental formula. It increases with arc current.
    3) The electric signal, into which the light of arc is converted, can be approximately regarded as stationary gaussian random process with constant component judging from the results of the measurement of amplitude density function.
    4) The space distribution characteristics of fluctuating and constant components depend on arc gene-rated condition and they show flat profile within the region of the obtained image if the relation of arc current and voltage is porper.
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  • Toyofumi Kitada, Nakatsugu Abe, Souzaburo Miyata
    1979 Volume 48 Issue 10 Pages 878-883
    Published: October 05, 1979
    Released: August 05, 2011
    High current density gas shielded arc welding process has been applied successfully to vertical joints of oil storage tank as low heat input and high efficient welding process. The toughness of the welds by this process has to be improved for lower temperature applications. This can be achieved by conducting the fundamental research on the relationship between the microstructure, hardness and toughness by varying major alloying elements and microalloying elements in the weld metals.
    Attentions were paid to classifying microstructures quantitatively, and the hardness levels were varied in the wide range.
    The main results are as follows:
    (1) Amount of acicular ferrite increase with increasing major alloying element for 180-225Hv of hardness levels, which results in improving toughness.
    (2) Niobium and Vanadium increase ferrite side-plate microstructure detrimental to toughness, and increase hardness by precipitation of Nb carbide and V carbide for stress relief treatment, which brings about poor toughness. The effects of Nb are influential as compared to V.
    (3) Boron increases acicular ferrite, consequently improves remarkably toughness. Stress relief treatment does not bring about precipitation hardening and fixes free nitrogen as BN precipitate, which is expected to result in improving toughness.
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